On a residential street in the Orange County suburb of La Palma, federal marshals and police officers on Friday descended on the suburban home of Christopher Jordan Dorner’s mother. The heavy weaponry and bulletproof vests used to serve a search warrant left no doubt: these officers were on high alert, looking for a man armed, dangerous and wanted throughout Southern California. But at the same time, residents of the orderly neighborhood were painting a much different picture of the suspect, remembering him as friendly and courteous.

That inconsistency is apparent in much of Dorner’s backstory. There’s the man who played on his college football team and is nothing but smiles on Facebook and in military and police photos. And then there’s Dorner the fugitive ex-cop, who in the past week has terrorized Southern California with a Rambo-style rampage targeting police officers and killing three people. Friends call him honorable and passionate, but emerging information about Dorner’s past suggests a conflicted, even disturbed figure.

“I know most of you who personally know me are in disbelief to hear from media reports that I am suspected of committing such horrendous murders and have taken drastic and shocking actions in the last couple of days,” Dorner allegedly wrote on his Facebook page in the days after police say he shot and killed the daughter of a retired LAPD captain and her fiancé. The former captain had represented him at a hearing on his 2009 dismissal from the police force. “You are saying to yourself that this is completely out of character of the man you knew who always wore a smile wherever he was seen.” Since then, Dorner is believed to have killed a Riverside police officer and wounded another, and to have grazed the head of a Los Angeles police officer.

Law-enforcement officials are now in the fifth day of a massive manhunt spanning the snowy mountains east of Los Angeles to the Mexican border. There have been few leads since they found Dorner’s burned-out truck last Thursday. On Sunday the city announced a $1 million reward for information leading to his arrest. And as police seek to protect fellow officers who might be targeted and search for clues to Dorner’s whereabouts, mental-health experts are trying to understand the personality disorder that could have lurked behind Dorner’s smile for years.

Former friends and neighbors willing to speak about Dorner have had nothing but good things to say. “He was a nice guy,” says Crystal Lancaster, who lives next door to the longtime residence of Dorner’s mother in La Palma. Another woman said Dorner waved to her only days before as she watered plants in her yard. “He was a very friendly guy, very pleasant,” says the neighbor, who asked to remain anonymous. No one answered the door at the home of Dorner’s mother.

Jaime Usera, Dorner’s college friend at Southern Utah University in the late 1990s, says he had great respect for him and never saw any violent or unstable tendencies. “He was a very principled man,” Usera, who is now an attorney in Oregon, tells TIME. “I liked him, enjoyed his company and considered him a friend. He had very strong convictions, and I mean that in the most positive way.” Neil Gardner, assistant athletic director at the university, was also complimentary. “He was a great guy,” says Gardner, who would travel and eat meals with Dorner when he was a reserve running back on the football team. “He was friendly. I wouldn’t say he was outgoing, but he certainly wasn’t shy. I have a positive memory of him.”

Dorner’s service in the Navy didn’t seem to provide any warning signs either. He earned the rank of Lieutenant in 2006 after joining four years earlier and served overseas in Bahrain. Dorner’s list of awards and decorations was long, including the National Defense Service Medal, the Iraq Campaign Medal, the Pistol Expert Medal and the Global War on Terrorism Service Medal, according to Navy documents. Clint Grimes, a Long Beach police sergeant who served in the Navy with Dorner, told the Daily Breeze that he was very intelligent, always followed military protocol and was always smiling.

Dorner’s past romantic relationships may tell a different story. An ex-girlfriend Ariana Williams said in court documents that he was a “severely and emotionally disturbed person,” according to the Associated Press. Williams, who only dated Dorner for several weeks, had warned other women against dating him in 2006 on a site called dontdatehimgirl.com, and Dorner filed a restraining order against her. Dorner was also married for less than a month in 2007 to a woman named April Carter, CBS News reported. One of Carter’s neighbors told TIME that Carter had been “embarrassed” about the marriage. And according to Carter’s former tenant Rachelle Brumley, Carter said she had never met anyone worth marrying. Carter didn’t return phone calls and didn’t answer the door at her Long Beach residence.

Dorner’s alleged Facebook manifesto is also far from levelheaded. In the document, the writer expresses remorse at not having shot a fellow officer in the head when he was with the LAPD after that officer used a derogatory word to describe black people. He expresses “concern” about prejudice and those who “victimize” innocent people, while at the same time promising to kill people. He also blames his dismissal from the LAPD for ruining his life and says it’s the motive for his killing spree.

That blame, the “highly self-referential” tone and Dorner’s brief, troubled romantic relationships are signs of a condition called narcissistic-personality disorder (NPD), says James Fallon, a professor of psychiatry and human behavior at UC Irvine’s medical school. That condition is characterized by an inflated sense of self-importance, little ability to feel empathy and reaction to criticism with rage, according to the U.S. National Library of Medicine. “It is pretty clear from the reports we have so far that his traits really line up well with NPD, but these also overlap with some related personality disorders including antisocial-personality disorder,” Fallon says. Asked why so many people from Dorner’s past might describe him as friendly, Fallon says “for people with these personality disorders, it is not odd at all that they are smiling and gregarious. It is part of the con job.”

Dorner was fired from the LAPD after a disciplinary board found he had made false statements against his training officer. The police force announced this weekend that it would reopen that case. Dorner reportedly had a temper and frequently filed complaints against other officers. But that conduct wasn’t enough to warrant suspicion that he could be capable of murder — especially four years after his termination. Dorner’s behavior before the shootings was more benign, for example, than that of other recent high-profile perpetrators. James Holmes of the Aurora, Colorado, movie theater massacre had told people he wanted to kill; Jared Loughner, the man who shot Congresswoman Gabrielle Giffords in Arizona, had been kicked out of college for disruptive behavior.

The unpredictability of Dorner’s alleged spree is partly what makes it so terrifying. “He left no paper trail of mental illness,” says UCLA psychology professor Paul Abramson. “In other cases, at least there’s some line of logic. This person doesn’t seem to fit that.”